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Coagulation

Coagulation laboratory tests

Factor XIII assay


Reviewer: Jeremy Parsons, M.D. (see Reviewers page)
Revised: 21 June 2012, last major update June 2012
Copyright: (c) 2002-2012, PathologyOutlines.com, Inc.

General
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Indications:
● Patients with familial bleeding disorder but normal PT and PTT and normal von Willebrand panel
● Factor XIII deficiency causes delayed bleeding after clot formation due to deficient crosslinking of the fibrin clot

Screening assay:
● Evaluates clot stability in 5M urea
● Add calcium to patient plasma to make it clot, incubate for 30 minutes at 37C, then place clot in 5M urea for 24 hours at room temperature
● Normal patients have stable cots, but patients with factor XIII deficiency of 1-2% of normal have clots that dissolve in urea
● Screening assay does not detect heterozygotes
● 2% acetic acid can also be used as a clot stability screening reagent, but will only detect patients down to 4% deficiency

Quantitative assay:
● Reference range is 70-140% of normal
● Detects values of 50% of normal (heterozygous deficiencies)
● Expensive and not readily available, factor XIII is activated by thrombin, attaches glycine ethyl ester to a peptide substrate, releasing ammonia detected by photometer
● High serum ammonia levels falsely decrease the result
● Newborns may have lower levels than adults

Additional references
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Parsons, J.C. Factor XIII Deficiency. LabQ 2012 (ASCP);CL-11:79

End of Coagulation > Coagulation laboratory tests > Factor XIII assay


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